There are prior vibratory-type marine sound sources, but such equipment has been heavy, bulky, clumsy and awkward to deploy behind a seagoing vessel. Certain prior hydraulically-actuated vibratory marine sound sources were attempted to be mounted directly on the stern of a seagoing vessel. However, action/reaction forces generated by such stern-mounted, hydraulically-driven, vibratory, sound equipment produced troublesome, disturbing and undesirable vibrations involving stern portions of the vessel itself. Such vibrations became severe in structural members, panels, braces and the like which happened to be vibrationally resonant with fundamental and/or harmonic (overtone) frequencies generated by a large, stern-mounted, powerful, hydraulically-driven vibratory sound source.
Attempts to use prior vibratory sound sources separated from the vessel itself and being towed through a body of water behind the vessel have experienced considerable difficulties. Their heavy weight and bulk have made them difficult to lift from shipboard over the stern and then lower into the water for deploying them. They similarly were difficult to retrieve from the water to return them onto shipboard.
Furthermore, large cross-sectional areas of prior marine seismic vibratory apparatus, i.e., their frontal areas, produced unacceptably large drag forces through water, thereby tugging backward against forward motion of towing vessels. Undesirable consequences of large drag forces are unduly large stresses in towing gear and wasteful large consumptions of fuel used in propelling towing vessels.
A sleek, fish-like configuration that produced minimum drag was described by the present inventor in U.S. Pat. No. 6,464,035 which is herein incorporated by reference. The disclosed device corrected many of the issues noted above however the device had minimal control in positioning the system at a specified depth and a flaw in pressure balancing. Accordingly, there is a need for a marine sound source system that improves depth positioning control, improves frequency response, improves energy efficiency and reliability through the reduction of unwanted accelerations, and provides a reduction in the risk of contamination of the surveyed body of water.